The invention concerns the respiratory apparatuses which are intended to protect persons on board an aircraft, in particular the technical flight crew, from the effects of depressurization at high altitude and/or from fumes or toxic gases.
More precisely, the invention concerns the respiratory apparatuses with a demand regulator with air dilution and the regulators for regulating the pressure and flow of respiratory gas.
A regulator for regulating the pressure and flow of respiratory gas generally comprises, connected to a nose-and-mouth mask:
inlet means for additional gas, generally oxygen, or highly oxygen-enriched air, and
an ejector for mixing dilution air with the additional gas and connected to an outlet supplying a user with diluted additional gas.
These respiratory apparatuses are supplied, at the inlet level, with additional gas delivered by pressurized oxygen cylinders, chemical generators, or generators by selective absorption and return of oxygen called OBOGS (acronym for On-Board Oxygen Generator System).
The regulators deliver a respiratory gas for which the course of the enrichment for a given flow as a function of altitude presents an inverse bell shape, that is to say the run of the solid-line curve in FIG. 1. Because of the characteristics of the ejector, the flow of additional gas (oxygen), at low altitude, is much greater than the flow corresponding to the necessary physiological minimum, which for its part increases in a monotonous manner as a function of the cabin altitude (dashed-line curve in FIG. 1).
The flow of additional gas (oxygen) delivered to the respiratory apparatus is too high relative to the requirements and is the cause of excessive consumption of additional gas (oxygen).
An object of the invention is in particular to make available a respiratory apparatus with a regulator for regulating the pressure and flow of respiratory gas, with which it is possible to reduce the flow of additional gas required.
This object is achieved, by virtue of a regulator of the type described above, additionally comprising, at the inlet of additional gas to the ejector, control means which are able to modify the cross section of passage of the additional gas to the ejector; these means can in particular switch the supply of additional gas between several inlet passages having different cross sections; for example, one of these passages corresponds to a flow called xe2x80x9ceconomyxe2x80x9d and has a smaller cross section than that of the other passage called xe2x80x9cfull flowxe2x80x9d.
This is because the passage of smaller cross section has a loss of charge which limits the flow of additional gas delivered to the respiratory mask (dotted-line curve in FIG. 1) to a value close to the physiological minimum necessary for a given altitude (dashed-line curve in FIG. 1).
Means are advantageously provided in order to guarantee the safety of the user without intervention on his part or by preventing false manoeuvres.
This object can be achieved in several ways. As an example, a regulator is provided which comprises safety means which have the following characteristics:
they prohibit switching of the supply of additional gas to the passage of smaller cross section when there is no delivery of dilution air (for example upon manual switching to what is called xe2x80x9c100%xe2x80x9d mode, corresponding to a delivery of pure additional gas to the respiratory mask), and
they prohibit the delivery of pure additional gas to the mask by cutting off the air admission, when the supply of additional gas is effected via the passage of smaller cross section.
The regulator according to the invention advantageously comprises the following characteristics in isolation or in combination:
the control means can be actuated manually;
it comprises an altimetric capsule for actuating the control means as a function of the altitude.
When the regulator is fitted on a respiratory mask with inflatable harness, it comprises a harness inflation actuator for bringing the supply of additional gas into communication with the inflatable harness in order to inflate it; the control means advantageously cooperate with the harness inflation actuator in order to switch the supply of additional gas to the xe2x80x9cfull flowxe2x80x9d passage when the harness inflation actuator is used to inflate the harness. For example, the control means switch the supply of additional gas to the xe2x80x9cfull flowxe2x80x9d passage under the effect of the pressure of the gas supplying the harness.
According to another aspect, the invention is a generator of enriched respiratory gas, comprising a pressure regulator according to the invention.
Other aspects, objects and advantages of the invention will become apparent on reading the following detailed description of a number of embodiments.
The invention will also be better understood with the aid of the attached drawings.